The objective of this research is development of a method to determine spatial distributions of targeted organic compounds in biological tissue. Such a capability would make possible rapid analysis of tissue for localization of toxins and pharmaceuticals, and quite possibly, their metabolites. Secondary ion mass spectrometry (SIMS) will be employed to obtain organic ion micrographs of the tissue. The spatial resolution which can be attained will be determined by the practical yield of secondary ions, that is, the number of analyte-characteristic secondary ions detected per incident primary ion. Instrumental capabilities will be optimized by rigorous application of ion optical design criteria to the entire secondary ion mass spectrometer. Methods of in situ chemical pretreatment of the sample will be developed for enhancing characteristic secondary ion emission from selected analytes. Choice of primary ion beam species and conditions will be investigated to optimize secondary ion yield. Tandem mass spectroscopy (MS/MS) will be employed so that characteristic ions can be resolved by their structure, in addition to their mass-to-charge ratios, as is currently practiced in SIMS. Data will be obtained using an existing IBM PC/XT data system, with off-line data manipulation and image processing performed by a DEC MicroVAX computer.